This proposal is divided into (1) study of the contribution of mast cell and eosinophil-dependent pathways to the pathogenesis of the human cutaneous blistering disorder bullous pemphigoid, and (2) isolation, characterization, and development of specific assays for components of the human neutrophil neutral peptide generating pathway, so as to permit study of this pathway in appropriate human cutaneous disorders. Neutrophil, eosinophil and lymphocyte chemotactic factors from bullous pemphigoid blister fluid will be purified and characterized so that their targets in human skin and their cell of origin may be determined. The cellular and humoral contribution to the regulation of histamine in bullous pemphigoid blister fluid will be studied. The chemical data will be correlated with the order of pathologic alterations as determined by electron microscopic and histopathologic study of developing skin lesions. Components of the neutrophil pathway for the generation of a neutral peptide mediator and the degradation of fibrinogen and fibrin will be fully characterized. The neutral peptide product will be purified, characterized, structurally defined and synthesized in vitro. The biology of components of this pathway will be studied and specific immunoassays will be developed for quantitation of each component in complex biologic fluids and detection in tissue.